Determining the body composition of an individual is of fundamental importance in many applications within the medical and fitness domains. An individual's personal parameters such as water, muscle or fat percentage play a key role to determine the health state of that individual. For example, determining the amount of water in the human body is especially important in a number of settings to prevent people from becoming dehydrated. However, current systems do not allow for the automatic measurement of the actual water percentage in the body without error, or even with small error. Consequently, this has to be determined or approximated manually. For example, nurses have to physically write down the amount of water a patient drinks and/or measure their urine to try to find out whether or not the patient's water balance is acceptable. This procedure is regularly practised, in intensive care stations, for example. This method is not only cumbersome, but also imprecise since it does not take into account other effects on the patient, such as sweating.
Therefore, having an approach or system that allows for the automatic and precise measurement of the actual composition of an individual's body is of key importance in medical and fitness applications. Some current systems for the analysis of body composition are based on bio-impedance. Bio-impedance (see for example, http://en.wikipedia.org/wiki/bioimpedance) measures the propagation features of an electric current through the human body. The propagation of electricity (electric current) depends on different parameters such as the signal frequency. However, the current systems based on bio-impedance are not precise enough to provide results of sufficient reliability. There exist a number of models to choose from, in order to find out the actual body composition of the patient. Although the choice of the correct model is crucial, it is not always evident, since it depends upon a number of parameters such as the age or gender of the individual being assessed. Additionally, bio-impedance based systems require a number of electrodes interconnected by wires that limits the user experience when designing wearable systems and makes the resulting scheme more complex to use and expensive. Finally, these systems are highly dependent on the user's body position when the measurements are taken. As a result, current systems do not allow for the automatic and precise measurement of the patient's parameters. Furthermore, the systems based on bio-impedance present several drawbacks such as the use of imprecise models or the need of many electrodes.
International Patent Application Publication WO 2007/113756 discloses a method and apparatus for determining hydration levels by measuring velocity change. In accordance with an example embodiment, an apparatus includes a transmitting transducer operative to transmit a mechanical wave. The apparatus also includes a receiving transducer operative to receive the mechanical waves transmitted from the transmitting transducer, wherein the transmitting transducer and the receiving transducer are disposed over a same side of a layer of tissue. The apparatus includes a processor operative to calculate a velocity of the mechanical wave in a medium, wherein the velocity is representative of a hydration level in the medium. While the technology disclosed in this Publication is an improvement over many known techniques, it still nevertheless requires an accurate measurement of distance between the two transducers to be taken, which can be difficult to achieve in many practical situations with a patient, and also requires that a velocity calculation be made of the wave, which can be affected by factors other than just the hydration level such as the pressure of the transducers on the tissue, the temperature, or the orientation of the muscle fibers.
It is therefore an object of the invention to improve upon the known art.